use anyhow::Result;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use tracing::info;

/// Schema manager for database metadata
#[derive(Debug)]
pub struct SchemaManager {
    cached_schemas: HashMap<String, DatabaseSchema>,
}

/// Database schema information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DatabaseSchema {
    pub database_name: String,
    pub tables: Vec<TableInfo>,
    pub views: Vec<ViewInfo>,
    pub functions: Vec<FunctionInfo>,
    pub indexes: Vec<IndexInfo>,
}

/// Table information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TableInfo {
    pub name: String,
    pub schema: String,
    pub columns: Vec<ColumnInfo>,
    pub primary_keys: Vec<String>,
    pub foreign_keys: Vec<ForeignKeyInfo>,
    pub indexes: Vec<String>,
    pub row_count: Option<u64>,
    pub table_size: Option<u64>,
}

/// Column information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ColumnInfo {
    pub name: String,
    pub data_type: String,
    pub is_nullable: bool,
    pub is_primary_key: bool,
    pub is_foreign_key: bool,
    pub default_value: Option<String>,
    pub max_length: Option<u32>,
    pub precision: Option<u32>,
    pub scale: Option<u32>,
    pub comment: Option<String>,
}

/// View information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ViewInfo {
    pub name: String,
    pub schema: String,
    pub definition: String,
    pub columns: Vec<ColumnInfo>,
}

/// Function information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FunctionInfo {
    pub name: String,
    pub schema: String,
    pub return_type: String,
    pub parameters: Vec<ParameterInfo>,
    pub definition: String,
}

/// Parameter information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ParameterInfo {
    pub name: String,
    pub data_type: String,
    pub direction: ParameterDirection,
}

/// Parameter direction
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ParameterDirection {
    In,
    Out,
    InOut,
}

/// Foreign key information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ForeignKeyInfo {
    pub name: String,
    pub column: String,
    pub referenced_table: String,
    pub referenced_column: String,
    pub on_delete: ReferentialAction,
    pub on_update: ReferentialAction,
}

/// Referential action
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ReferentialAction {
    NoAction,
    Restrict,
    Cascade,
    SetNull,
    SetDefault,
}

/// Index information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct IndexInfo {
    pub name: String,
    pub table: String,
    pub columns: Vec<String>,
    pub is_unique: bool,
    pub is_primary: bool,
    pub index_type: String,
}

impl SchemaManager {
    /// Create a new schema manager
    pub fn new() -> Self {
        Self {
            cached_schemas: HashMap::new(),
        }
    }
    
    /// Load database schema
    pub async fn load_schema(&mut self, database_name: &str) -> Result<&DatabaseSchema> {
        info!("Loading schema for database: {}", database_name);
        
        // TODO: Implement actual schema loading from database
        // This is a placeholder implementation
        
        let schema = DatabaseSchema {
            database_name: database_name.to_string(),
            tables: vec![],
            views: vec![],
            functions: vec![],
            indexes: vec![],
        };
        
        self.cached_schemas.insert(database_name.to_string(), schema);
        
        Ok(self.cached_schemas.get(database_name).unwrap())
    }
    
    /// Get cached schema
    pub fn get_schema(&self, database_name: &str) -> Option<&DatabaseSchema> {
        self.cached_schemas.get(database_name)
    }
    
    /// Refresh schema cache
    pub async fn refresh_schema(&mut self, database_name: &str) -> Result<()> {
        info!("Refreshing schema cache for: {}", database_name);
        
        // Remove from cache and reload
        self.cached_schemas.remove(database_name);
        self.load_schema(database_name).await?;
        
        Ok(())
    }
    
    /// Get table information
    pub fn get_table_info(&self, database_name: &str, table_name: &str) -> Option<&TableInfo> {
        self.get_schema(database_name)?
            .tables
            .iter()
            .find(|table| table.name == table_name)
    }
    
    /// Search tables by name
    pub fn search_tables(&self, database_name: &str, pattern: &str) -> Vec<&TableInfo> {
        if let Some(schema) = self.get_schema(database_name) {
            schema.tables
                .iter()
                .filter(|table| table.name.contains(pattern))
                .collect()
        } else {
            vec![]
        }
    }
    
    /// Get all table names
    pub fn get_table_names(&self, database_name: &str) -> Vec<String> {
        if let Some(schema) = self.get_schema(database_name) {
            schema.tables.iter().map(|table| table.name.clone()).collect()
        } else {
            vec![]
        }
    }
    
    /// Clear schema cache
    pub fn clear_cache(&mut self) {
        self.cached_schemas.clear();
    }
    
    /// Get cache statistics
    pub fn get_cache_stats(&self) -> SchemaCacheStats {
        SchemaCacheStats {
            cached_databases: self.cached_schemas.len(),
            total_tables: self.cached_schemas.values()
                .map(|schema| schema.tables.len())
                .sum(),
            total_views: self.cached_schemas.values()
                .map(|schema| schema.views.len())
                .sum(),
        }
    }
}

/// Schema cache statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SchemaCacheStats {
    pub cached_databases: usize,
    pub total_tables: usize,
    pub total_views: usize,
}

impl Default for SchemaManager {
    fn default() -> Self {
        Self::new()
    }
}
